In recent ten years, with rapid development of a horizontal well, an extended-reach well, a multilateral well and other complex structural wells as well as “offshore oil production on land” and shale gas development, and upon the requirements of a drilling technology to reduce the efficiency, reducing the cost, improving the drilling capacity, etc., under severe environments and complicated geological conditions, the research about the rotation guidance drilling technology has been developed both in China and abroad. The rotation guidance drilling technology is a new cutting-edge automatic drilling technology. Proved by drilling practices in China and abroad, when the rotation guidance drilling technology is promoted and applied in a horizontal well, an extended-reach well, a highly-deviated well and a three-dimension multi-target well, the drilling speed is improved and the drilling failure is also reduced, thereby reducing the drilling cost. A rotation guidance drilling tool serves as a core of a rotation guidance drilling system and decides operating features and the operating capacity of the rotation guidance drilling system.
A rotation guidance technology is used to drill a well with a rotary table (or top drive) rotary drill stem and realizes a corresponding guidance function while drilling. The rotation guidance technology has the following advantages of: eliminating sliding drilling, reducing torque and friction drag, enhancing hole quality, improving hole cleanness, increasing penetration rate, reducing equivalent circulation density, selecting optimal drilling parameters to obtain maximum penetration rate, reducing risk of differential pressure sticking, making the selection for drilling performance of a drill bit be superior to the selection for the guidable property of the drill bit, realizing directional control over the whole drilling course of the extended-reach well, drilling a majority of wells having high difficulty well track at low risk and saving drilling time. Moreover, the well depth limit may reach 15 km, and the drilling cost is low. Therefore, the rotation guidance drilling technology is an inevitable direction in the development of modern guidance drilling technologies.
At present, three major oil companies abroad, BakerHughes, Schlumberger and Halliburton have respectively formed PowerDriveSRD, AutoTrakRCLS and Geo-Pilot rotation guidance drilling systems for respective commercial application by means of various ways, and the foundational difference of the three systems is that downhole drilling tools are different, which fully explains that the rotation guidance drilling tool serves as a core of a rotation guidance drilling system. The two former systems may be classified into one system, namely push-the-bit rotation guidance drilling system; and the latter system belongs to a point-the-bit rotation guidance drilling system. The push-the-bit rotation guidance system has large lateral force and high deflection rate, but holes drilled by rotation guidance have large doglegs and track fluctuation and are not smooth, and a drill bit and a drill bit bearing are worn more seriously. The point-the-bit rotation guidance system has the capability of drilling relatively smooth holes with smaller friction drag and torque, may make use of a relatively high drilling pressure, has relatively high penetration rate, and is conducive to developing the performances of a drill bit, the lateral load borne by the drill bit and a bearing thereof is relatively small, the ultimate displacement increases, but the deflection rate is relatively low. At present, the push-the-bit rotation guidance system has basically matured in technology, however, the point-the-bit rotation guidance system still is at a start stage.
It was lately that the research in this field began to develop, and it was in full swing in the 1990s. A technical team led by academician, Yinao Su successfully developed a CGDS-1 near-bit geosteering rotary drilling system, 15 wells being applied in oil fields, such as Jidong and Liaohe. Moreover, a research team led by professor, Shaohuai Zhang, also gained breakthroughs in the aspect of rotation guidance drilling in cooperation with Shengli Oil Field of Sinopec. But a majority of researches focused on push-the-bit rotation guidance drilling, and the search on point-the-bit rotation guidance drilling was at a bottlenecked state in China.